Portable terminals, such as smartphones and tablets, provide a variety of useful functions to users through a lot of applications. Therefore, the portable terminals are evolving toward devices that provide various types of information, in addition to voice call information, via various functions. Such a portable terminal is connected to an external device and outputs data to the external device or receives data from the external device by a data Input/Output (I/O) function.
To provide the data I/O function, the portable terminal and the external device should be connected in a specific connection scheme, such as Universal Serial Bus (USB) connectivity and Mobile High-Definition Link (MHL) connectivity. If the external device supports MHL connectivity and USB connectivity, the portable terminal recognizes a USB device of the external device based on a resistance of a USB IDentifier (ID) pin.
However, since USB ID pins are limited resources, ACcessory Detection (ACD) values corresponding to the resistance values of the USB ID pins cannot be defined for all supported accessories. As a consequence, a portable terminal recognizes only a limited number of external devices, and may not recognize all external devices supporting USB connectivity.
FIG. 1 illustrates a configuration of a communication system according to the related art.
Referring to FIG. 1, the communication system includes a portable terminal 101 and an external device 103. When the external device 103 is connected to the portable terminal 101 via a Universal Serial Bus (USB) cable 105, the external device 103 provides its specific function to the portable terminal 101. The external device 103 is called an accessory and may be any of a TeleVision (TV), a monitor, a beam projector, a keyboard, a touch screen, a Personal Computer (PC), an audio player, an auxiliary battery, and any other similar and/or suitable electronic device. For example, if the external device 103 is a TV, then the external device 103 may provide a multimedia play function of receiving multimedia data from the portable terminal 101 and displaying the received multimedia data.
When the portable terminal 101 is connected to the external device 103 via the USB cable 105, the portable terminal 101 measures a resistance of a pin corresponding to a USB IDentifier (ID), from among a plurality of pins included in a connector of the portable terminal 101. The portable terminal 101 determines the external device 103 based on the measured resistance, referring to a table tabulating ACcessory Detection (ADC) values with respect to predetermined resistance values of USB IDs. Then the portable terminal 101 recognizes the external device 103 by performing a USB host function.
The USB host function refers to a function that enables operation between portable terminals such as a Personal Digital Assistant (PDA), an MP3 player, and a portable phone, without intervention of a main computer. For example, the USB host function may include a data exchange function between the portable terminal 101 and the external device 103, and a battery charging function of the portable terminal 101, when the external device 103 is an auxiliary battery.
FIG. 2 is a table that tabulates ADC values versus the resistance values of USB ID pins according to the related art.
Referring to FIG. 2, a table 201 that tabulates ADC values versus the resistance values of USB ID pins includes ADC values 203 allocated to a plurality of accessories. For example, if a USB ID resistance is 28.7 KΩ, the portable terminal 101 may detect an ADC value of 0x0E mapped to the USB ID resistance 28.7 KΩ. If determining that the external device 103 corresponds to Accessory 1 mapped to the ADC value 0x0E, then the portable terminal 101 may recognize the external device 103 by performing the USB host function.
However, since USB ID pins are limited resources, ADC values corresponding to the resistance values of USB ID pins cannot be defined for all supported accessories. Consequently, the portable terminal 101 may recognize a limited number of accessories, because not all accessories support USB connectivity. For example, the portable terminal 101 may recognize only five types of accessories 203 preset in the table 201 listing ADC values versus the resistance values of USB ID pins, and thus, may not recognize other types of accessories.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.